Polymeric films

ABSTRACT

Multi-layer polymeric films having at least one skin layer comprising at least one polyhydroxyether component or a combination of at least one polyhydroxyether component and at least polyester component are provided. The multi-layer films exhibit advantages such as high surface energy contributing to improved printability, barrier properties, and metallization. Additionally, the films exhibit improved adhesion between the skin layer and other layers of multi-layer film structures. In certain embodiments, the at least one skin layer incorporates from about 70 wt. % to about 100 wt. % of the at least one polyhydroxyether component or the combination of the at least one polyhydroxyether component and the at least one polyester component. The combination of the at least one polyhydroxyether component and the at least one polyester component incorporates from about 1 wt. % to about 99.0 wt. % of the at least one polyhydroxyether component and from about 1 wt. % to about 99 wt. % of the at least one polyester component.

FIELD OF THE INVENTION

This disclosure relates to multiple layer polymeric films including atleast one skin layer incorporating at least one polyhydroxyethercomponent or a combination of a polyhydroxyether component and apolyester component.

BACKGROUND OF THE INVENTION

Films with skin layers incorporating polyesters are known. Such filmsare widely used in the packaging industry. Generally, the polyester skinlayers are inexpensive, clear, offer high surface energy, and are stablein orientation processes.

U.S. Pat. No. 5,324,467 to Anderson describes coextrusion or extrusioncoating processes for the preparation of an oriented multi-layerlaminate film, consisting of at least three layers, including apolypropylene layer, an adhesive layer of polar modified polyolefin, anda glycol or acid modified copolyester layer. The multi-layer film isprepared by uniaxially or biaxially stretching castings. It is disclosedthat the film has good heat sealability and high gas barrier.

U.S. Pat. No. 5,637,366 to Davis, et al. and U.S. Pat. No. 6,221,191 toDavis, et al. disclose biaxially oriented polypropylene core layer filmswith multiple layer film cap layers. The cap layer is laminated orcoated onto the core layer. The cap layer includes at least onepolyester layer and at least one tie layer interposed between thepolyester layer and the PP core. The cap layer is provided on a machinedirection oriented uniaxially oriented polypropylene core layer. Theresulting composite is stretched in a transverse direction.

U.S. Pat. No. 6,472,081 to Tsai, et al. discloses an orientedmulti-layer film combination including a propylene homopolymer orcopolymer core layer, a metallizable skin layer including a materialselected from an ethylene-vinyl alcohol copolymer (EVOH), poly(vinylalcohol) (PVOH), and polyester. An adhesive tie layer made from amaterial selected from a maleic anhydride modified propylene homopolymeror copolymer, a high density polyethylene (HDPE), and an ethylene-vinylacetate (EVA) copolymer. The adhesive tie layer is disposed between thecore layer and the skin layer.

U.S. Pat. No. 6,027,776 to Mueller discloses a multi-layer filmincorporating an interior layer of ethylene/alpha-olefin copolymer; afirst exterior layer of a material selected from a propylene homopolymeror copolymer, a propylene homopolymer or copolymer blended with anelastomer, HDPE, and a copolyester. A second exterior layer includes amaterial selected from a polyamide, a copolyamide, polyester,copolyester, HDPE, PP, propylene/ethylene copolymer, and polycarbonate.A first adhesive layer is provided between the interior layer and thefirst exterior layer while a second adhesive layer is provided betweenthe interior layer and the second exterior layer. The adhesive layersare anhydride-modified ethylene/methyl acrylate copolymers. It isdisclosed that this film is used to produce flexible pouches for thepackaging and administration of medical solutions.

U.S. Pat. No. 6,663,974 to Kelch, et al. discloses a non-orientedmulti-layer film with a polyolefin core incorporating 40 wt. % or lessof homogeneous ethylene/alpha-olefin. A modified polyolefin tie layer isprovided on each side of the core layer with an adhesive layer on atleast one tie layer. The adhesive layer contains a polar-modifiedpolyolefin and a polyester, copolyester, or polyester and copolyesterblend. It is disclosed that this multi-layer film has utility as aprotective coating for metal surface.

BRIEF DESCRIPTION OF THE INVENTION

This disclosure relates to multi-layer polymeric films having at leastone skin layer comprising at least one polyhydroxyether component or acombination of at least one polyhydroxyether component and at least onepolyester component. The multi-layer films exhibit advantages such ashigh surface energies contributing to improved printability,coatability, sealability, barrier properties, and metallization.Additionally, the films described herein exhibit improved adhesionbetween the skin layer and an adjacent layer of multi-layer filmstructures.

In certain embodiments, the at least one skin layer incorporates fromabout 70 wt. % to about 100 wt. % of the at least one polyhydroxyethercomponent or the combination of the at least one polyhydroxyethercomponent and the at least one polyester component. Additionally, incertain embodiments, the combination of the at least onepolyhydroxyether component and the at least one polyester componentincorporates from about 1 wt. % to about 99.0 wt. % of the at least onepolyhydroxyether component and from about 1 wt. % to about 99 wt. % ofthe at least one polyester component.

The at least one skin layer may be adhered directly to an adjacentfunctional film layer or adhered to an adjacent functional film layerthrough the use of an adhesive tie layer. Adhesion between the skinlayer and the functional layer or the tie layer is improved as comparedto adhesion typically exhibited between conventional skin layers andadjacent film layers. The at least one skin layer described herein mayalso improve processability of films incorporating the skin layer.Conventional polymeric films incorporating skin layers incorporatingcertain materials, particularly polyesters, have a tendency to stick toheated rollers and other equipment elements used to orient the films.Films including the skin layers incorporating at least onepolyhydroxyether component, as described herein, exhibit a reducedtendency to stick to the processing equipment thereby leading to bettergauge control and optics of the polymeric films described herein. Thepresence of the at least one polyhydroxyether component in the skinlayer may disrupt stress localization and strain-induced crystallizationwhen the films described herein are produced through biaxialorientation. This disruption may lead to improved optical and gaugeuniformity of the films described herein.

DETAILED DESCRIPTION OF THE INVENTION

It is observed that films incorporating certain materials, particularlypolyesters, are deficient in interlayer adhesion strength and exhibit avariety of processability problems due to crystalline structures andsurface stickiness. For example, polyester containing skin layersgenerally suffer from poor interlayer adhesion to adjacent tie layersand functional layers of dissimilar materials such as polyolefin basedpolymers. Additionally, in commercial scale orientation processes,coextruded polyester skin layers often stick to the heated rolls in themachine direction orientation section, thus increasing haze anddeteriorating adhesive and optical properties of the film.

Coating processes used in combination with film orientation processesseek to eliminate the sticking in the machine direction orientationsection by introducing the polyester skin layer after the machinedirection orientation section. However, the polyester skin layer stillproduces optical and thickness nonuniformity and sticking to equipmentssuch as tenter frame clips during the transverse direction orientationprocess. Moreover, when the multi-layer film produced by the extrusioncoating process is exposed to heat environment during converting or enduser application processes, it distorts or curls severely by thepresence of uniaxially and biaxially oriented layers in the same filmstructure.

This disclosure relates to multiple layer polymeric films. The filmsdescribed herein incorporate at least one skin layer and a filmsubstrate incorporating at least one polymeric film layer. The skinlayer exhibits beneficial performance properties while at the same timeexhibiting a level of adhesion to the adjacent film substrate sufficientto make the multiple layer film structure useful in a wide variety ofapplications. For example, the films described herein are useful forproducing packages and label structures.

The at least one skin layer incorporates at least one polyhydroxyethercomponent or a combination of at least one polyhydroxyether componentand at least one polyester component. It has been found that such skinlayers may exhibit many, if not all, of the advantages associated withconventional polyester skin layers, such as barrier properties and highsurface energies that contribute to improved printability, coatability,sealability, and metallization of the skin layers. Moreover, the atleast one skin layer exhibits adhesion to an adjacent film substrate atlevels superior to conventional polyester skin layers. For example, incertain embodiments of the films described herein, the at least one skinlayer exhibits a peel strength, measured by a TMI slip/peel tester atthe 180° angle tensile testing mode, to an adjacent layer that may be acore layer or a tie layer, that is greater than 40.0 g/cm. In otherembodiments, the peel strength is greater than 50.0 g/cm. In still otherembodiments, the peel strength is greater than 60.0 g/cm. In additionalembodiments, the peel strength is greater than 70.0 g/cm.

The at least one skin layer may be incorporated into multi-layer filmstructures having a wide variety of additional layers, including thefilm layer adjacent to the skin layer.

In certain embodiments, the at least one skin layer incorporates fromabout 70 wt. % to about 100 wt. % of at least one polyhydroxyethercomponent or a combination of at least one polyhydroxyether componentand at least one polyester component. In other embodiments, the at leastone skin layer incorporates from about 80 wt. % to about 100 wt. % of atleast one polyhydroxyether component or a combination of at least onepolyhydroxyether component and at least one polyester component. Instill other embodiments, the at least one skin layer incorporates fromabout 90 wt. % to about 100 wt. % of at least one polyhydroxyethercomponent or a combination of at least one polyhydroxyether componentand at least one polyester component.

In turn, in certain embodiments, the combination of the at least onepolyhydroxyether component and the at least one polyester componentincorporates from about 1 wt. % to about 99 wt. % of the at least onepolyhydroxyether component and about 1 wt. % to about 99 wt. % of the atleast one polyester component. In additional embodiments, thecombination of the at least one polyhydroxyether component and the atleast one polyester component incorporates from about 1 wt. % to about50 wt. % of the at least one polyhydroxyether component and about 50 wt.% to about 99 wt. % of the at least one polyester component. In otherembodiments, the combination of at the least one polyhydroxyethercomponent and the at least one polyester component incorporates fromabout 1 wt. % to about 30 wt. % of the at least one polyhydroxyethercomponent and about 70 wt. % to about 99 wt. % of the at least onepolyester component. In still other embodiments, the combination of atthe least one polyhydroxyether component and the at least one polyestercomponent incorporates from about 5 wt. % to about 20 wt. % of the atleast one polyhydroxyether component and about 80 wt. % to about 95 wt.% of the at least one polyester component.

In certain embodiments, the at least one skin layer described herein mayhave a thickness of about 0.1 μm to about 25 μm. In other embodiments,the at least one skin layer described herein may have a thickness ofabout 0.2 μm to about 15 μm. In additional embodiments, the at least oneskin layer described herein may have a thickness of about 0.2 μm toabout 5 μm.

The at least one polyester component for use in the at least one skinlayer described herein may be selected from a wide variety of polyestersand blends thereof. Exemplary suitable polyesters for selection as theat least one polyester include homopolyesters, copolyesters, and blendsthereof. Specific exemplary homopolyesters include poly(ethyleneterephthalate) (PET), poly(trimethylene terephthalate) (PTMT),poly(butylene terephthalate) (PBT), poly(ethylene naphthalate) (PEN),polylactic acid (PLA), polycarbonate (PC),poly(1,4-cyclohexylenedimethylene terephthlate) (PCT), polyester baseliquid crystalline polymers (LCP), and blends thereof. In certainembodiments, the polyester is selected from PET, PLA, PEN, and blendsthereof. In other embodiments, the polyester is selected from PET, PLA,and blends thereof. In still other embodiments, the polyester is PET.

Exemplary suitable copolyesters for selection as the at least onepolyester component include glycol or acid modified polyesters having atleast three different monomeric units. Specific exemplary copolyestersare copolyesters of terephthalic acid (TPA), ethylene glycol (EG), and1,4-cyclohexylenedimethylene (CHDM), poly(ethylene terephthalate glycol)(PETG), copolyesters of isophthalic (IPA) and terephthalic acids (TPA),diethylene glycol (DEG), EG and CHDM, copolyesters of bisphenol-A of IPAand TPA (polyarylate), copolyesters of IPA, TPA, EG and butane diol, andblends thereof. In certain embodiments, the copolyester is selected fromcopolyesters of terephthalic acid (TPA), ethylene glycol (EG), and1,4-cyclohexylenedimethylene (CHDM), PETG, copolyesters of isophthalic(IPA) and terephthalic acids (TPA), diethylene glycol (DEG), EG andCHDM, and blends thereof. In other embodiments, the polyester isselected from terephthalic acid (TPA), ethylene glycol (EG), and1,4-cyclohexylenedimethylene (CHDM), PETG, and blends thereof. In stillother embodiments, the polyester is PETG.

Suitable exemplary commercially available polyesters include PEThomopolymer VORIDIAN® from Eastman Chemical Company and RYNITE® fromE.I. du Pont de Nemours and Company, PTMT homopolymer CORTERRA® fromShell Chemical, PBT homopolymer VALOX® from GE plastics and CRASTIN®from E.I. du Pont de Nemours and Company, PLA homopolymer PLA POLYMERfrom Cargill Dow LLC, PEN homopolymer TEONEX® from Teijin Corporation,PC homopolymer LEXAN® from GE Plastics, polyester base LCP VECTRA® andVECTRAN® from Ticona Engineering Polymers, PCT homopolymer THERMIX® fromE.I. du Pont de Nemours and Company, and copolyester EASTAR® andEMBRACE® from Eastman Chemical Company and CRYSTAR® from E.I. du Pont deNemours and Company.

The polyhydroxyether component may be selected from a wide variety ofpolyhydroxyethers and combinations thereof. Polyhydroxyethers havependant hydroxyl moieties and aromatic ether moieties in the repeatingunit. In certain embodiments, the polyhydroxyethers includepoly(hydroxyl amino ether), poly(hydroxyl amide ether), poly(hydroxylether of Bisphenol A) (“phenoxy”), and blends thereof. Other suitablepolyhydroxyethers include poly(hydroxyl amino ether) containing atertiary amine unit, which participates in hydrogen-bonding interactionand poly(hydroxyl amide ether) containing two amide groups as part ofthe polymer repeat unit. The synthetic routes and further examples ofsuitable polyhydroxyethers are disclosed in U.S. Pat. No. 5,134,218 toBrennan, et al. and U.S. Pat. No. 5,275,853 to Silvis, et al.

Exemplary suitable phenoxides may have a molecular weight (MW) of 15,000to 55,000 g/mol, a degree of polymerization (n) is about 50 to 300, amelt index at 220° C. (428° F.) and 2.16 kg of 0.5 g/10 min to 5.0 g/10min, and a volatile content of 0.01 wt. % to 3.0 wt. % as determined at220° C. (428° F.) for 1 hour.

Exemplary suitable polyhydroxyethers are poly(hydroxyl amino ether) andpoly(hydroxyl amide ether) that are commercially available from DowChemical Company under the designation BLOX®. They may have a melt indexof 0.25 g/10 min to 20 g/10 min at 190° C. (374° F.) and 2.16 kg and avolatile content 0.01 wt. % to 5.0 wt. % as determined at 220° C. (428°F.) for 1 hour. In certain embodiments, the resins may have a low meltindex below 5.0 g/10 min and a low volatile content below 2.0 wt. % asdetermined at 220° C. (428° F.) for 1 hour.

As discussed in Brennan et al., Macromolecules, 28, 6694, (1995), thehydroxyl and amide (or amine) groups in polyhydroxyethers are two of themost important contributors to a high gas barrier and a high adhesivereactivity in polymers. The m-phenylene units in poly(hydroxyl aminoether) and poly(hydroxyl amide ether) are also preferred for a low gaspermeability and a high adhesive reactivity. Polymers that contain them-phenylene backbone segment have lower oxygen transmission and betteradhesion than their p-phenylene counterparts. The “kinked” structure ofpolymers containing the 1,3-phenylene unit allows their backbones toadopt more preferential chain conformations for enhanced packagingefficiency than backbones dominated by more rigid p-phenylene segments.

As discussed in Coleman et al., Macromolecules, 25, 4414, (1992), thepolyhydroxyether is generally miscible with the polyester at themolecular level through intermolecular π-electron interaction as well asester exchange reactions between the pendant hydroxyl groups of thepolyhydroxyether and the ester linkages of the polyester. Therefore,polyhydroxyethers do not form particles or isolated regions when the atleast one polyhydroxyether component and the at least one polyestercomponent are blended. For this reason, when a combination of apolyhydroxyether component and a polyester component are used to produceskin layers in film structures produced in orientation processes, thepolyhydroxyethers typically will not create voids in the skin layer.

The at least one polyhydroxyether component and the at least onepolyester component may be combined by blending or compounding the atleast one polyhydroxyether and the at least one polyester. In certainembodiments, the blends are produced by blending pellets of the at leastone polyhydroxyether and the at least one polyester. Thereafter, theblended pellets may be fed to an extruder for formation of the skinlayer. In certain embodiments, the skin layer is coextruded with otherlayers of adjacent film substrate to which skin layer is adhered.

As discussed above, the at least one skin layer produced as describedherein exhibits improved adhesion to the adjacent film substrate. Incertain embodiments, the adjacent film substrate incorporates acoextruded polyolefin layer. In other embodiments, the adjacent filmsubstrate to which the at least one skin layer is adhered incorporatesan oriented coextruded polypropylene film layer. In still otherembodiments, the adjacent film substrate incorporates a coextrudedbiaxially oriented polypropylene layer.

In general, polyesters have little or no chemical and physicalinteractions with polyolefin such as polyethylene and polypropylene.Therefore, an adhesive tie layer is typically used to tie together thepolyester layer and the polyolefin layer. The adhesive tie resin mayinclude copolymers having ester and olefin segments and functionalizedpolymers that react chemically with polyesters. Polyester components mayalso be modified to have more functional groups in order to facilitateadhesion between a film layer incorporating at least one polyestercomponent and an adjacent polyolefin layer.

In other embodiments, as discussed above, the at least one skin layermay be adhered to another functional film layer of the adjacent filmsubstrate through the use of a tie layer incorporating a tie resin.Suitable adhesive tie resins include polar modified polyolefins. Polarmodified polyolefins include olefin polymers having a polar monomercopolymerized therein, olefin polymers or copolymers grafted with acidsor anhydrides, or derivatives thereof. Exemplary polar modifiedpolyolefins include ethylene copolymers, and their ethylene acrylatecopolymers (EA), anhydride-modified EA, acid terpolymers containingester and acrylic functionalities, polar-modified PP such as maleicanhydride grafted polypropylene (PP-MAH), glycidyl methacrylate modifiedPP (PP-GMA), random terpolymers of ethylene, acrylic ester and glycidylmethacrylate, and blends thereof. These polymers may include at leastone elastomer or polar modified elastomer as a toughener or tougheners,such as ethylene-propylene copolymers (EPM), polar modified EPM such asEPM-MAH, ethylene-butylene copolymers, polar modified ethylene-butylenecopolymers, ethylene-octene copolymers, polar modified ethylene-octynecopolymers, styrene-butadiene-styrene copolymers (SBS), polar modifiedSBS such as SBS-MAH, styrene-ethylene-butylene-styrene copolymers(SEBS), polar modified SEBS such as SEBS-MAH, and blends thereof. Theether linkage and pendant —OH groups of polyhydroxyethers promotewetting and bonding to these polar modified substrates. Therefore, thehydroxyl and carboxyl groups of the skin layer polymers react rapidlywith the functional group of the tie resins and provide a secondaryintermolecular bond, therefore increasing interlayer adhesion andintermolecular cohesion.

In addition to improved adhesion to adjacent film layers, the at leastone skin layer described herein may also improve processability of filmsincorporating the skin layer. Conventional polymeric films incorporatingpolyesters have a tendency to stick to rollers and other equipmentelements used to process the films. Films including the skin layerincorporating at least one polyhydroxyether and layers incorporating atleast one polyhydroxyether and at least one polyester exhibit a reducedtendency to stick to such processing equipment thereby leading to bettergauge control and optics of the polymeric films described herein. Thepresence of the at least one polyhydroxyether in the skin layer may alsodisrupt stress localization and strain-induced crystallization when thefilms described herein are produced through biaxial orientation. Thisdisruption may lead to improved optical and gauge uniformity of thefilms described herein.

The polymeric substrates to which the at least one skin layer isadjacent may be any single or multi-layer polymeric material that can beformed into a film. The substrate can be clear or opaque. Additionally,the substrate may be colored or have a matte finish. The opacity ofopaque films may be achieved by cavitating, creating voids, in one ormore layers of the polymeric film substrate or by other means. Forexample, cavitation may be achieved through the use of organic orinorganic voiding agents or though production techniques independent ofthe use of voiding agents. Exemplary thermoplastic materials for use inthe single and multiple film layers include any polyolefin such aspolypropylene, polyethylene, polybutene, polystyrene, polyvinylchloride, ethylene containing copolymers such as ethylene-propylenecopolymers, ethylene containing terpolymers such asethylene-propylene-butene terpolymers, polar modified polyolefin, andblends thereof. Other suitable film materials include polyesters,including but not limited to homopolyesters, copolyesters, polyesterbased LCP, polyamide including oriented nylon, ethylene-vinyl alcoholcopolymer (EVOH), and blends thereof. In still other embodiments, thepolymeric material selected from the group of propylene homopolymers,propylene copolymers, ethylene homopolymers, ethylene copolymers, polarmodified polyolefins, polyesters, polyamides, polystyrenes,ethylene-vinyl alcohol copolymers, and blends thereof. In certainembodiments, the polymeric material for a core layer is selected from apolymeric material selected from propylene homopolymers, propylenecopolymers, and blends thereof.

In films structures having three or more layers, a skin layer oppositethe skin layer incorporating the at least one polyhydroxyether or the atleast one polyhydroxyether and the at least one polyester may beprovided. Exemplary opposite skin layers comprise polyethylene,including medium and high-density polyethylene, polypropylene,copolymers of propylene, and ethylene and terpolymers of propylene,ethylene and butylene, and blends thereof. In certain embodiments, thepolymeric substrate includes a second skin layer opposite the first skinlayer comprising a polymeric material selected from propylenehomopolymers, propylene copolymers, ethylene homopolymers, ethylenecopolymers, ethylene/propylene/butene terpolymers, polar modifiedpolyolefins, and blends thereof.

The various layers of the multiple layer film structures describedherein may incorporate processing aids or inorganic particulates such astitanium dioxide or void initiating agents to enhance the whiteness orcolor of the substrate or to enhance anti-blocking properties. Exemplaryvoid initiators and techniques are disclosed in U.S. Pat. No. 5,885,721to Su et al. and U.S. Pat. No. 6,168,826 to Su et al. Exemplaryadditional additives are slip, anti-block, and anti-static agents thatare well known in the art and used to improve substrate functionalityand properties. Additionally, as mentioned previously, the substrate maybe metallized.

The film structures described herein include a film substrateincorporating at least one polymeric layer having a first surface and asecond surface and at least one skin layer as described above. Thesubstrate may incorporate single or multiple film layers. For example,the multi-layer film may be a 3-layer structure with the substrate beinga 2-layer polymeric film that comprises a core layer having the skinlayer adjacent to a first surface of the core layer and an outer layeropposite the skin layer adjacent to the second surface of the corelayer. In such embodiments, the core layer may comprise polypropylene,polyethylene, polar modified polyolefins, and blends thereof. In otherembodiments, the film structure may be a 4-layer structure with thesubstrate being a 3-layer polymeric film which comprises an adhesive tielayer imposed between the skin layer and the first surface of the corelayer and an outer layer adjacent to the second surface of the corelayer. In certain of these embodiments, the core layer may comprisepolypropylene, polyethylene, and blends thereof. In other embodiments,the film structure may be a 5-layer structure with the substrate being a4-layer polymeric film which comprises a core layer, two intermediatelayers adjacent to the central core layer, and with the skin layeradjacent to a first intermediate layer and an outer layer adjacent to asecond intermediate layer. In certain of these embodiments, theintermediate layer adjacent to the skin layer may comprise polarmodified polyolefins and the core layer may comprise polypropylene.

In certain embodiments, the multiple layer film structures describedherein may incorporate two skin layers incorporating the at least onepolyhydroxyether component or a combination of at least onepolyhydroxyether component and the at least one polyester component, asdescribed herein. Such films may be particularly useful in applicationsrequiring printing, coating, sealing, lamination, or metallization onboth sides at the same time. The two skin layers may have the same ordifferent application such as printing on one side and coating on theother side.

A particular type of thermoplastic film which can be advantageously usedin the substrate of the film structures described herein is molecularlyoriented isotactic polypropylene. After extrusion of the substrate, forexample, utilizing conventional extrusion techniques, the film is heatedand molecularly oriented by stretching it in both the longitudinal andtransverse directions. The resulting oriented film exhibits greatlyimproved tensile and stiffness properties. Typically polyolefin resins,such as polypropylene, are extruded through a flat sheet extruder die ata temperature ranging from between about 200° C. (392° F.) to about 260°C. (500° F.), casting the film onto a cooling drum and quenching thefilm. The sheet is then stretched about 3 times to about 7 times in themachine direction (MD) orienter followed by stretching about 5 times toabout 10 times in the transverse direction (TD) orienter. For additionaldetails regarding biaxially oriented film processes, see U.S. Pat. No.3,380,868 to Moser and U.S. Pat. No. 2,736,066 to Chren.

The film structures in accordance with this disclosure may be orientedor hot-blown films made from any of a number of processes. The orientedfilms may be manufactured in a variety of processes including biaxialorientation, machine direction orientation (MDO), double bubble,simultaneous longitudinal and transverse orientation (LISIM®), tapebubble, trapped bubble or tenter framing. The use of linear motors todirectly propel tenter clips to effect simultaneous longitudinal andtransverse orientation is disclosed in U.S. Pat. No. 4,853,602 to Hommeset al. Hot-blown films are typically manufactured in a simple bubbleprocess.

Experimental Evaluations

Films incorporating skin layers as described herein were produced andthe performance of the films was evaluated in a series of experimentalevaluations. In these evaluations, 5-layer film structures were preparedwith a 1.0 μm skin layer on one surface of the films. A comparative filmwas prepared with the skin layer incorporating a copolyester PETGcommercially available from Eastman Chemical under the designationEASTAR® 6763. The skin layers of the exemplary film structures inaccordance with this disclosure incorporated a blend of PETG and apoly(hydroxyl ether of Bisphenol A) commercially available from InChemCorp. under the designation Phenoxy PKFE in the weight ratios listed inTable I below. All blends for the skin layers were prepared by blendingPETG and PKFE pellets. The skin layers were adjacent to a 2.0 μm tielayer produced from a PP-MAH and commercially available from MitsuiChemical under the designation Admer® 1179A. The tie layer was adjacentto a 14.0 μm polypropylene core layer produced from a polypropylenehomopolymer commercially available from ExxonMobil Chemical Companyunder the designation PP 4712E2. Adjacent to the opposing surface of thecore layer was a 2.0 μm intermediate layer also produced from PP 4712E2.Finally, a 1.0 μm sealant layer produced from anethylene-propylene-butene terpolymer commercially available from ChissoPetrochemical under the designation XF 7700 was provided adjacent to theintermediate layer. The films were produced by coextruding the variousfilm layers at 260° C. (500° F.) onto a casting drum maintained at 43.3°C. (109.94° F.). The cooled extrudate was then stretched 4.7 times inthe machine direction at roller temperatures (T_(MDO)) set in astaggered manner: 110° C. (230° F.) for the sealant skin and 98° C.(208.4° F.) to 110° C. (230° F.) for the blend skin (see Table I below).Thereafter, the extrudate was stretched 8 times in the transversedirection at temperatures of about 160° C. (320° F.). The peel strengthof resultant films was measured with a TMI slip/peel tester at the 180°angle tensile testing mode. Specimens were 2.54 cm wide and 15.2 cmlong. The surface of the blend skin was carefully taped by 2.54 cm wide3M 610 Scotch® tape to prevent film tear during the peeling test. Theblend skin was then delaminated by pulling or snapping the tape on theleading edge. The peel strength was measured subsequently. Oxygentransmission rate was measured at 23° C. (73.4° F.) and 0% RH. Theproperties of the films are reported in Table I.

TABLE I Peel PETG/Phenoxy T_(MDO) Haze Strength OTR Example ratios (°C.) (%) (g/cm) (cc/m²/24 hr) 1 100/0 wt. % 110/98  1.10 37.9 1660(Comparative) 2  95/5 wt. % 110/98  1.08 45.2 1550 3  95/5 wt. % 110/1011.11 41.7 1603 4  95/5 wt. % 110/105 1.09 42.3 1696 5 85/15 wt. %110/98  1.10 73.2 1243 6 85/15 wt. % 110/110 1.08 71.8 1299 7 80/20 wt.% 110/98  1.12 78.3 1350 8 80/20 wt. % 110/110 1.21 76.4 1420

The comparative film having a skin layer incorporating only PETG stuckto machine direction orientation rolls, causing optical defects andscratches on the surface. The film also showed optical nonuniformity,for example, hazy bands, along the machine direction. Sticking was notobserved on the machine direction orientation rolls for the filmscontaining phenoxy in the skin layers. T_(MDO) was increased to 110° C.(230° F.) without sticking at phenoxy concentration above 10 wt. %. Thesame T_(MDO) for both the blend skin layer and the sealant skin layereliminated film nonuniformity associated with gradient of MD orientationtemperature across the thickness direction of the film. Filmsincorporating the combinations of the at least one polyester and the atleast one polyhydroxyether exhibited substantially higher peel strengthand lower oxygen transmission rates, with equivalent haze as compared tothe comparative film. The film comprising the PETG/PKFE blend skincomprising 15 wt. % phenoxy (Example 5) increased peel strength by about100% and reduced oxygen transmission by about 25%, as compared toComparative Example 1.

In certain embodiments, the films described herein have oxygentransmission rates below 1,700 cc/m²/24 hr at 23° C. (73.4° F.) and 0%RH. In other embodiments, the films described herein have oxygentransmission rates below 1,600 cc/m²/24 hr at 23° C. (73.4° F.) and 0%RH. In still other embodiments, the films described herein have oxygentransmission rates below 1,500 cc/m²/24 hr at 23° C. (73.4° F.) and 0%RH.

With respect to the various ranges set forth herein, any upper limitrecited may, of course, be combined with any lower limit for selectedsub-ranges.

All patents and publications referred to herein are hereby incorporatedby reference in their entireties.

Although films and processes for producing the films described hereinhave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made without departingfrom the spirit and scope of the films and processes described, asdefined by the following claims.

1. A multilayer polymer film comprising: (a) a film substrate comprisinga tie layer, said tie layer comprising a tie resin having acid oranhydride functional groups; and (b) a first skin layer comprising atleast one polyhydroxyether having hydroxyl groups; wherein saidmultilayer polymer film is biaxially oriented, and wherein the peelstrength between said first skin layer and said film substrate isgreater than 40.0 g/cm.
 2. The multilayer polymer film of claim 1,wherein said at least one polyhydroxyether is selected from the groupconsisting of poly(hydroxyl amino ether), poly(hydroxyl amide ether),poly(hydroxyl ether of Bisphenol A), and blends thereof.
 3. Themultilayer polymer film of claim 2, wherein said first skin layerfurther comprises at least one polyester.
 4. The multilayer polymer filmof claim 3, wherein said at least one polyester is selected from thegroup consisting of homopolyesters, copolyesters, and blends thereof. 5.The multilayer polymer film of claim 3, wherein said at least onepolyhydroxyether is selected from the group consisting of poly(hydroxylamino ether), poly(hydroxyl amide ether), and blends thereof, said atleast one polyester is poly(ethylene terephthalate glycol).
 6. Themultilayer polymer film of claim 1, wherein said polyhydroxyethercomprising about 70 wt. % to about 100 wt. % of said first skin layer.7. The multilayer polymer film of claim 3, wherein said combination ofat least one polyhydroxyether and at least one polyester comprises fromabout 1 wt. % to about 99 wt. % of said at least one polyhydroxyetherand from about 1 wt. % to about 99 wt. % of said at least one polyester.8. The multilayer polymer film of claim 3, wherein said combination ofsaid at least one polyhydroxyether and at least one polyester comprisesfrom about 1 wt. % to about 30 wt. % of said at least onepolyhydroxyether and from about 70 wt. % to about 99 wt. % of said atleast one polyester.
 9. The multilayer polymer film of claim 3, whereinthe oxygen transmission rate of the multilayer polymer film produced isbelow 1,700 cc/m²/24 hr at 23° C. (73.4° F.) and 0% RH.
 10. Themultilayer polymer film of claim 1, wherein said film substrate furthercomprises a first polymeric material selected from the group consistingof propylene homopolymers, propylene copolymers, ethylene homopolymers,ethylene copolymers, polar modified polyolefins, polyesters, polyamides,polystyrenes, ethylene-vinyl alcohol copolymers, and blends thereof. 11.The multilayer polymer film of claim 10, wherein said film substratefurther comprises a second polymeric material selected from the groupconsisting of propylene homopolymers, propylene copolymers, ethylenehomopolymers, ethylene copolymers, polar modified polyolefins,polyesters, polyamides, polystyrenes, ethylene-vinyl alcohol copolymers,and blends thereof.
 12. The multilayer polymer film of claim 1, whereinsaid film substrate further comprises a core layer, said core layercomprising propylene homopolymers, propylene copolymers, or blendsthereof.
 13. The multilayer polymer film of claim 12, wherein said tielayer is disposed between the core layer and the first skin layer. 14.The multilayer polymer film of claim 1, wherein said peel strength isgreater than 50.0 g/cm.
 15. The multilayer polymer film of claim 1,wherein said film substrate further comprises a second skin layeropposite the first skin layer, the second skin layer comprising a secondpolymeric material selected from the group consisting of propylenehomopolymers, propylene copolymers, ethylene homopolymers, ethylenecopolymers, ethylene/propylene/butene terpolymers, polar modifiedpolyolefins, and blends thereof.
 16. The multilayer polymer film ofclaim 1, wherein said multilayer polymer film is opaque.
 17. Themultilayer polymer film of claim 1, wherein said at least one substratelayer is voided.
 18. A package comprising said multilayer polymer filmof claim 1, wherein said multilayer polymer film is formed into apackage.
 19. A label comprising said multilayer polymer film of claim 1,wherein said multilayer polymer film is formed into a label.
 20. Amultilayer polymer film comprising: (a) a film substrate comprising atleast one tie layer, said tie layer comprising a tie resin having acidor anhydride functional groups; (b) a first skin layer comprising acombination of at least one polyhydroxyether and at least one polyester,said polyhydroxyether having hydroxyl groups, wherein said at least onepolyhydroxyether is selected from the group consisting of poly(hydroxylamino ether), poly(hydroxyl amide ether), and blends thereof; whereinsaid multilayer polymer film is biaxially oriented, wherein the peelstrength between said first skin layer and said film substrate isgreater than 40.0 g/cm; and whereby the oxygen transmission rate of themultilayer polymer film produced is below 1,700 cc/m²/24 hr at 23° C.(73.4° F.) and 0% RH.
 21. The multilayer polymer film of claim 20,wherein at least one polyester is poly(ethylene terephthalate glycol).22. The multilayer polymer film of claim 20, wherein said combination ofat least one polyhydroxyether and at least one polyester comprises fromabout 1 wt. % to about 99 wt. % of said at least one polyhydroxyetherand from about 1 wt. % to about 99 wt. % of said at least one polyester.23. A package comprising said multilayer polymer film of claim 20, saidmultilayer polymer film is formed into a package.
 24. A label comprisingsaid multilayer polymer film of claim 20, said multilayer polymer filmis formed into a label.